Throttle control for two-stage carburetor



May 28, 1957 H. A. CARLSON THROTTLE CONTROL FOR TWO-STAGE CARBURETOR 2 Sheets-Sheet 1 Filed March 29. 1954 INVENTOR. HAROtD A.CARLSON BY WKW ATTORNEY May 28, 1957 H. A. cARLsoN 2,793,343

THROTTLE CONTROL FOR TWO-STAGE CARBURETQR Filed March 29, 1954 2 Sheets-Sheet 2 F IG. 4. INVENTOR.

HAROLD A. CARL SON ATTQRNEY United States Fatent THROTTLE CONTROL: FOR .TWO-ST AGE CARBURETOR 'Harold A. I Carlson, Brentwood, -Mo.,= assignor, by mesne assignments, I to :AGF Industries, II Incorporated, New

York, N. 'Y., ,a rcorporationadf New Jersey Application March 29,11 954,fSerial' No. 419,381

. 3- Claims. -(Cl. 261- 23) T his invention relates t- 'mllllEl-Sta:g6 carburetion sys- I tems. for internal combustion engines and. consists more paiticularly in novel means for causing opening of the -secondary throttle '--va-lve at the proper time and firm closing of this-valve When' the-primary throttle valve is closed.

There has been difiiculty in -the kiesigning of multistage carburetorsin insuring firmclosing of the secondary throttle during idling, so as to minimize leakage' around the valves, without undesirably-increasing resistance to opening the secondary throttle I either automatically or "-manually in response to opening 'of t he primary throttle.

In the currentlypopular four bar-rel=earburetors-the ill J efiects of -excessive, -air leakage at idle, 'whi'ch may -be caused by sticking-==throttle valves, =becomes-a serious problem.

:Where the -secondary throttles are;.opened'--bya'suction motor which-- responds =to-suct-ion-variations in the primary induction conduit; the secondary throttles may be closed by linkage connecting I the same to the primary throttles, .as in' Ericson et a1. Patent No.2;2-69,930 "or-Bicknell Patent No.2, 640,472. "A copendi-ngapplieation 'Serial No.

410,299, filed Februar y 1 5, 1 9-54, -in-the-narne-of=the present inventor: and another as joint -=i-nventors suggests I vention,

iFig. his :a side vview. oi a. two-stagescarburetor.embodying the invention, portions being removed and others broken away and sectioned for clearer illustration.

Fig. 2 is a side view of the lower portion of the carburetor.

Fig. 3 is a view similar to Fig. 2, but showing the primary throttle valve opened sufficiently so that opening of the secondary throttle valve is initiated.

Fig. 4 is a view similar to Figs. 2 and 3, but showing both throttle valves fully opened.

The carburetor shown has primary and secondary mixture conduits 6 and 7 with venturi tube arrangements 8 and 9. These primary conduits may be duplicated, as is the case in four-barrel carburetors now in use. Main fuel nozzles 10 or 11 discharge, respectively, into the primary and secondary venturi arrangements and these communicate with fuel bowl portions 12 and 13 through metering orifice elements 14 and 15. Fuel for idling is supplied through passages 16 and 17 discharging through ports 18 and 19 adjacent and posterior to primary and secondary throttle valves 20 and 21 when closed. These fuel systems supply fuel through the idling ports when their associated throttle valves are closed or nearly closed, and through the main fuel nozzles when the throttle valves are opened, the discharges from the interconnected 2,793,843 Patented May 28, 19. 57

*main and I idling systems blending during opening move- :ment of the throttle-valves, 'as is Welliknown. Asuitable accelerating pump (not; shown) may be provided.

For starting,- achoke valve-25 is providedinthe air in- -let portionofpri-mary intake-conduitd' and controlled by 'suitable automatic choke control mechanism located in housing 26 mountedon the outsideofthe' air inlet or air horn-portion of thecarburetor. Fuel is-supplied to'con- --stant-leve1 bowl "portions '12 and 13 through ;'the usual --threadedinlet27.- --Primary throttle valve-20 is manually controllable by -means of a; lever "2'8 having an aperture 29 in the free end-jhermf for connection by the usual -*-1ink-age --to the acceleraton-pedal 'located in the drivers compartment. A---throttle-returnspring is-indicated'at30 for causing closing of the primary throttle valve-jzwhen the accelerator pedal is releasedby the -operator. The closed,-norma1 idling position ;of-'the-prirnary throttle is determined 'by *means of 'a-n-adjustable stop, screw 31 mounted on-the side of the '10W6I,"ihr0til6 body-portion --of-the carburetor antl an arm 32*for1ning a portion of '-throt'tle operating arm 28. i

Secondary throttle valvefll 1 is-ope ra te'd-by aj'SUCtlOn motor including a diaphr'agm i lficlamped between housing portions'- 36=and -3'l--to form diiferential pressure chambers*38 and 39'on opposite sidesthereof (Fig-1). =Casing portion 36 -is shownformed integrallywithihe lower throttle body portion of the carburetor and "includes a "double=w'a'lle'd =-structure- 40 forming a *linkagechamber lll' into whieh one end-er secoridary throttle valve shaft 0 42 -=-extends. arm fi rigid withshaft 42withgin chamber AL is connecte'd by -a link -44-to an actuating'rod '45 I 'centrally secured=-to:-'diaphragrn by -means of washers 46. Motor-=ehamber 38 istconnected by a passage 47,

i chamber-=41, and a--eonnecting;passage =48 to the-outlet 35 portion of primarymixture conduit 6-posterior to throttle valve 20 therein. Ghamber fl; in -practice,' is sealedby a cover '49 (Figs; 2, 3 and- 4) secured-to wall=:-bymeans I of screws 50.

The t other motor -'chamber' 39 is connected by A means of a-suction passage '54' to wenturi arrangement inthe tprimary mixture conduit,' in ithis case, to t;he5"throat'-por- ':ti on of the larger 0f the two -venturi tubes shown.

Secondary :throttleshaft 42 extends throughlinkage ichamberi ll' and' is journ'aled inzcover 49 thereon andat its: extremity 1 rigidly mounts an operating lever 55' ad- :rjustably-secured inposition on the shaft by-bolt-Sfi. Lever .55 shasan arm 57=:coopera ting with-adjusting-screw'i58--re- ..ceived: i-n fixed rib' 59 to determine the idling position -';of '1seeondary throttlewalve disk 21. I A coiled tensionspr-ing 60 connects a lug 61 on secondary throttle shaft arm 55 and an arm 62 on primary throttle shaft arm 28 for urging the secondary throttle valve closed variably in accordance with the position of the primary throttle valve.

In operation, during idling, the outlet portion of primary intake conduit 6 will be exposed to relatively high suction, While Venturi tube arrangement 8 will be exposed to a much higher pressure, substantially atmospheric, except during starting when choke valve 25 is closed, so as to cause the suction motor to apply firm closing force to secondary throttle valve 21 through two way linkage 415, 44, 43. This force is supplemented by tension spring 60 which is at its greatest stress when both throttle valves are closed, as shown in Fig. 2. As primary throttle valve 20 is opened and the speed of the associated engine increased, the suction in intake conduit 6 posterior to throttle 20 and in motor chamber 35 will sharply decrease while the pressure in venturi arrangement 8 and motor chamber 39 will gradually decrease so that, ultimately, the pressure in motor chamber 39 will be sufficiently less than that in motor chamber 38 to reverse the motor action and cause secondary throttle valve to start to open, as in Fig. 3. The suction motor and its operat- 3. ing suction connections are calibrated so that such initiation of opening of the secondary throttle valve occurs at the desirable speed for initiating second stage operation of the carburetion system. Thereafter, during increasing speed of the engine, at normal temperature, diaphragm 35 will continue its leftward movement against spring 30, and the secondary throttle valve will continue to open and, ultimately, both throttle valves will reach their full open positions, as in Fig. 4. However, during cold start ing and warmup, with the choke valve in a restricting position, there will be insuflicient pressure differential in the motor chambers to cause the secondary throttle to open. When the primary throttle valve is closed and/ or the speed of the engine decreases, pressure conditions in suction motor chambers 38 and 39 will approach balance and then reverse, ultimately, causing firm closing of the secondary throttle valve and elimination of the second stage operation.

Thus, suction motor chamber 38 which is the higher pressure chamber during opening movement of the secondary throttle valve, becomes a lower pressure chamber during idling to insure firm and positive closing of the secondary throttle valve. Such closing is produced, of course, without affecting the force necessary to open the secondary throttle valve, as, for instance, by increasing the size of the suction motor, as would be the case where the secondary throttle valve is urged closed by a spring. Exclusive use of all modifications as come within the scope of the appended claims is contemplated.

I claim:

1. In a multi-stage carburetor having primary and secondary mixture conduits, venturis in said conduits, fuel nozzles in said venturis, a primary throttle having an operating shaft journaled in said primary mixture conduit,

- and a secondary throttle having an operating shaft journaled in said secondary mixture conduit, the combination of a suction motor for operating said secondary throttle comprising a flexible diaphragm and first and second air-tight chambers on opposite sides of the flexible diaphragm, a third air-tight chamber enclosing the journal for said secondary throttle shaft, a common wall forming a partition between said second and third chambers, and an operating shaft slidably mounted in said wall and interconnecting said diaphragm and said secondary throttle shaft, said carburetor having a suction passage extending from the venturi in said primary mixture conduit to said first air-tight chamber on one side of said diaphragm, a suction passage in said wall, and a suction passage providing for communication between said primary mixture conduit posterior of said primary throttle and said third chamber, whereby said flexible diaphgram is subject on one side to the suction in the venturi in said primary mixture conduit and on the other side to the suction in said primary mixture conduit posterior to said primary throttle.

2. In a multi-stage carburetor having primary and secondary mixture conduits, venturis in said conduits, fuel nozzles in said venturis, a primary throttle having an operating shaft journaled in said primary mixture conduit, and a secondary throttle having an operating shaft journaled in said secondary mixture conduit, the combination of a suction motor for operating said secondary throttle comprising a movable pressure-responsive member and means providing air-tight enclosures on opposite sides of said pressure-responsive member, one end of said secondary throttle shaft extending into one of said enclosures, and means in said one enclosure interconnecting said pressure-responsive member and said one end of the secondary throttle shaft, said carburetor having a suction passage providing for communication between said primary mixture conduit posterior of said primary throttle and said one enclosure, a suction passage providing for communication between the venturi in said primary mixture conduit and the other enclosure, and spring means connected between the primary and second ary throttles for biasing the secondary throttle in closing direction with maximum force when the primary throttle is closed.

3. In a multi-stage carburetor having primary and secondary mixture conduits, venturis in said conduits, fuel nozzles in said venturis, a primary throttle having an operating shaft journaled in said primary mixture conduit, and a secondary throttle having an operating shaft journaled in said secondary mixture conduit, the combination of a suction motor for operating said secondary throttle comprising a movable pressure-responsive member and means providing air-tight enclosures on opposite sides of said pressure-responsive member, said carburetor having a suction passage providing for communication between said primary mixture conduit posterior of said primary throttle and said one enclosure, a suction passage providing for communication between the venturi in said primary mixture conduit and the other enclosure, and spring means connected between the primary and secondary throttles for biasing the secondary throttle in closing direction with maximum force when the primary throttle is closed.

References Cited in the file of this patent UNITED STATES PATENTS 

